This invention relates generally to the heat transfer field and more specifically to a means for uniformly cooling thermo-plastic polymers across a large cross-sectional area to prevent thermal degradation.
While the invention may be advantageously utilized to reduce thermal degradation and waste losses, the invention finds particular utility in the reduction of waste from reliquified polycondensation polymers.
In conventional recycling and retrieval, reliquified polymer scrap and the like is poured into large cooling and storage containers. Since only the outer portions of these containers are exposed to air currents and other cooling media, non-uniform cooling occurs resulting in thermal degradation of substantial amounts of the cooling polymer liquid since the outer skin of the cooling polymer in the container forms an insulation barrier blocking further core cooling. Maintaining the core at elevated temperatures for too long results in thermal degradation with the production of large amounts of commercially useless polymer waste.
This low thermal stability of some thermoplastic polymers may be attributed to the presence of reactive groups and chain units, e.g., --OH, --Cl, RCO--, which may be eliminated from the molecule in the form of water, hydrogen chloride, alcohol and ammonia. Thermal degradation may well be promoted by the presence of excess acidic groups or constituents, e.g. excess dicarboxycylic acid in polycondensation products. Other undesired results include the production of the noxious or toxic gases.
Although means for cooling polymer products or reliquified polymer scraps are known, the present invention represents a substantial improvement over the conventional apparatus by avoiding thermal degradation by providing more uniform cooling of the liquid polymer while also providing a large volume container that is easy to handle, transport and store.